/*
 * 二分法求根（4分）
 */

#include <stdio.h>
#include <math.h>

float getvalue(float x) {
	return x * x * x - x - 1;
}

int main() {
	setbuf(stdout, NULL);

	float low, high, mid;

	scanf("%f,%f", &low, &high);

	mid = (low + high) / 2;
	while (fabsf(getvalue(mid)) >= 0.000001) {
		if (getvalue(low) < 0 && getvalue(high) > 0 &&
		    getvalue(mid) > 0) {
			high = mid;
			mid = (low + high) / 2;
		}
		if (getvalue(low) < 0 && getvalue(high) > 0 &&
		    getvalue(mid) < 0) {
			low = mid;
			mid = (low + high) / 2;
		}
	}

	printf("x=%6.2f\n", mid);

	return 0;
}
